Computer Associates BABNWUP900NE6 Administration Guide - Page 45

Defining Data-transfer Requirements Reconciling Data Transfer Requirements and Resources If the preliminary calculations outlined in the preceding sections show that your required data transfer rate is feasible given your existing infrastructure, you may be able to stop here. However, preliminary calculations usually uncover conflicts between stated requirements and available time and resources. If minbandwidth is the amount of data that can be sent in a given time through the narrowest, slowest bottleneck in the path from the backup source to the backup media and if backupwindow is the time available, then the backup process is governed by the following equation: datatransferred = backupwindow × minbandwidth In our example, we have a 5-hour window, fast storage devices, and 100Base-T Ethernet. So the Ethernet LAN is our weakest link, and the following equation is true: datatransferred = 5 hrs × 36 GB/hour = 180 GB Therefore, to back up 1 Terabyte of data, you have to do at least one of the following tasks: ■ Increase the amount of time available to back up data. ■ Increase the bandwidth available at the narrowest part of the data path. ■ Reduce the size of datatransferred by backing up our 1 Terabyte in a series of smaller, independent operations. The following sections suggest several possible alternatives that will achieve one or more of the above tasks. Widening the Data Path If you cannot decrease the amount of data that you need to move in the time available, then a possible solution is to increase the available bandwidth. You can do this either on the network that links data hosts to the BrightStor ARCserve Backup server or in the hardware that stands between the server and the backup media. Planning 2-7